1. Technical Field
The present invention relates to a throttle assembly for controlling the flow(amount of the flow) of intake air in an internal combustion engine, as well as a throttle sensor for detecting the degree of opening of a throttle valve used in the throttle device.
2. Background Art
Heretofore, an electronically controlled throttle assembly has practically been used wherein the operation of a throttle valve in an engine is controlled by an electrically-driven actuator (e.g., a DC motor or a stepping motor).
The electronically controlled throttle assembly controls the throttle valve angle (throttle valve opening) to an optimum value according to the state of an engine and in accordance with a signal indicative of the degree of opening of an accelerator pedal or a traction control signal. To this end, a sensor for detecting the angle of the throttle valve, what is called a throttle sensor (also called an opening meter or a throttle position sensor) is attached to a throttle body.
As the throttle sensor there generally is adopted a potentiometer type sensor, wherein a brush (slider) adapted to rotate together with a throttle valve shaft slides on a resistor, thereby outputting a potential difference signal (sensor detection signal) corresponding to the degree of opening of a throttle valve.
As throttle sensors of this type so far used there are known, for example, such throttle sensors as are disclosed in Japanese Patent Laid Open Nos. 7-343878 and 9-32588, wherein a resistor and a wiring pattern of a potentiometer are formed on a substrate. The substrate is attached to a cover of a receptacle portion containing a reduction gear mechanism. A brush is attached to a flat surface of a driven gear (or a rotor) mounted on a throttle valve shaft. In this type of a throttle sensor, the brush slides on a resistor and a conductor both formed on the substrate (a flat surface). Since the driven gear is used also as a moving element to which the brush of the potentiometer is attached, the number of components used can be so much reduced.
It is an object of the present invention to provide a throttle device capable of contributing to reducing the number of components of a throttle sensor, capable of reducing the manufacturing cost and simplifying the assembling work, and further capable of ensuring high accuracy and reliability of the sensor.
For achieving the above-mentioned object the present invention basically proposes the following throttle assemblies:
(1) A throttle assembly comprising a throttle body having a throttle valve, an electrically-driven actuator for actuating the throttle valve, and a sensor for detecting the degree of opening of the throttle valve,
wherein the sensor is constituted by a potentiometer whose output varies according to the rotation of a throttle valve shaft and which comprises a slider (also called a brush) and a resistor, the slider being adapted to slide on the resistor and disposed on one end side of a throttle valve shaft so that a tip end thereof faces in a radial direction of the throttle valve shaft, the resistor being formed as an arcuately curved surface (what is called a curved resistor), and a wall portion which holds the curved resistor is formed by molding integrally with a cover which covers the one end side of the throttle valve shaft in the throttle body.
According to a preferred example of the above throttle device (1), the peripheral resistor holding portion (wall portion) is formed by molding integrally with the cover, as described above, and the slider is attached to a peripheral portion of a gear (a driven gear as a final-stage gear in a reduction gear mechanism) mounted on the throttle valve shaft.
(2) A throttle assembly comprising a throttle body and, as components mounted to the throttle body, a throttle valve for controlling the flow of intake air in an internal combustion engine, an electrically-driven actuator for actuating the throttle valve, a reduction gear mechanism for the actuator, and a sensor for detecting the degree of opening of the throttle valve,
wherein one end of a throttle valve shaft is projected outwards from a side wall of the throttle body, the reduction gear mechanism and the sensor are disposed on a side face of the throttle body on the projecting side of the throttle valve shaft,
a bearing which supports one end of the throttle valve shaft on the projecting side of the throttle valve shaft, out of bearings which support the throttle valve shaft, is a ball bearing, a bearing located on the opposite side of the throttle valve shaft is a cap-shaped plain bearing, and one bearing boss of the throttle valve shaft is covered with the plain bearing.
(3) A throttle sensor for detecting the degree of opening of a throttle valve which controls the flow of intake air in an internal combustion engine,
wherein the throttle sensor is constituted by a potentiometer whose output varies according to the rotation of the throttle valve, the potentiometer comprising a slider adapted to rotate integrally with a throttle valve shaft and a resistor on which the slider slides, the resistor being connected at one end thereof to a positive-side terminal of a power supply and at an opposite end thereof to a ground-side terminal, the position at which the resistor contacts the slider is an output point for taking out an output voltage, and an auxiliary resistor (or resistors) is connected either between one end of the resistor and the positive-side terminal of the power supply or between the opposite end of the resistor and the ground-side terminal, or both. In other words, an auxiliary resistor is provided at one end or at each of both ends of the resistor which is a component of the potentiometer.